1. Field of the Invention
The present invention relates in general to the field of hologram production and display and, more particularly, to hologram production on plastic substrates.
2. Description of the Related Art
One-step hologram (including holographic stereogram) production technology has been used to satisfactorily record holograms in holographic recording materials without the traditional step of creating preliminary holograms. Both computer image holograms and non-computer image holograms may be produced by such one-step technology. In some one-step systems, computer processed images of objects or computer models of objects allow the respective system to build a hologram from a number of contiguous, small, elemental pieces known as elemental holograms or hogels. To record each hogel on holographic recording material, an object beam is conditioned through the rendered image and interfered with by a reference beam. Examples of techniques for one-step hologram production can be found in the U.S. Patent Application entitled xe2x80x9cMethod and Apparatus for Recording One-Step, Full-Color, Full-Parallax, Holographic Stereograms,xe2x80x9d Ser. No. 09/098,581, naming Michael A. Klug, Mark E. Holzbach, and Alejandro J. Ferdman as inventors, and filed on Jun. 17, 1998, which is hereby incorporated by reference herein in its entirety.
In general, the holographic recording materials used in the fabrication of holograms include photopolymerizable compositions, dichromated gelatin, and silver halide emulsions. These holographic recording materials are typically placed on a glass substrate before used in hologram production equipment (e.g., a xe2x80x9cholographic printerxe2x80x9d). Glass is a useful substrate because of its good optical properties (e.g., high transmission, low distortion, low birefringence) and because of other beneficial mechanical properties including flatness, dimensional stability, scratch resistance, and chemical inertness.
However, because glass is relatively heavy and fragile, it is typically an unsuitable substrate for final placement of the holographic recording material, shipping of the finished hologram, and display of the finished hologram. This is particularly true for large format holograms or hologram tiles whose size is typically on the order of several feet.
Consequently, producers of holograms often prepare the hologram with the holographic recording material coupled to a glass substrate. The preparation typically includes both recording the hologram (i.e., exposing the holographic recording material to a suitably prepared interference pattern formed by one or more coherent light sources) and developing, curing, or fixing the holographic recording material, which can include, for example, exposing the holographic recording material to an ultraviolet light source and heating the holographic recording material. As is well known to those having ordinary skill in the art, these post-processing steps (e.g., developing, curing, or fixing the holographic recording material) depend in large part upon the type holographic recording material used.
Once the hologram has been prepared, it is often removed from the glass substrate, and placed on a plastic substrate that is stronger and lighter than the glass substrate, and thus more suitable for transporting and displaying the finished hologram. Unfortunately, the process of removing the finished hologram from the glass substrate and placing it on a plastic substrate introduces multiple handling steps that consume inordinate amounts of time. Moreover, the process risks the integrity of the hologram, increases the likelihood that the holographic recording material will be damaged (e.g., torn or scratched), and often leads to unwanted distortion of the image produced by the hologram.
Accordingly, it is desirable to eliminate steps from the hologram fabrication procedure in order to provide added efficiency, reduced costs, and higher quality final products.
It has been discovered that a holographic recording material coupled to a plastic substrate can be exposed to an interference pattern formed by at least one coherent light source, and subsequently processed, thereby eliminating the need to transfer the holographic recording material from a glass substrate to the plastic substrate. Additionally, by performing a post-exposure heating step in a liquid bath, the formation of unwanted bubbles between the plastic substrate and the holographic recording material is at least in part prevented.
By performing the exposure and post-processing of the holographic recording material on the same substrate that will be used for final mounting and display, there is less opportunity for contaminant introduction, handling stress and image artifact introduction. Plastic substrates also allow for pre-exposure and post-exposure flexibility so that curved substrate images can be made. Plastic substrates can be easily made with other features such as colors, textures, and coatings that are useful for various types of holographic displays. Plastic substrates are lighter than glass substrates, thereby requiring less work to move in the holographic exposure system. This can result in shorter total exposure times and reduced vibrational artifacts since the force needed to move the substrate can be less than that of glass. The final product is lighter and less fragile than glass.
Accordingly, one aspect of the present invention provides a method of producing a hologram on a plastic substrate. A holographic recording material layer coupled to the plastic substrate is provided. The holographic recording material layer coupled to the plastic substrate is exposed to an interference pattern formed by at least one coherent light source. The exposed holographic recording material layer coupled to the plastic substrate is heated while the exposed holographic recording material layer coupled to the plastic substrate is in one of a liquid bath and a steam bath.
Another aspect of the invention provides a hologram comprising a plastic substrate and an exposed holographic recording material layer coupled to the plastic substrate. The exposed holographic recording material layer includes an interference pattern formed by at least one coherent light source, wherein the exposed holographic recording material layer coupled to the plastic substrate has been heated in one of a liquid bath and a steam bath.
Still another aspect of the present invention provides another method of producing a hologram on a plastic substrate. A holographic recording material layer coupled to the plastic substrate is provided along with a barrier layer coupled to the holographic recording material layer. The holographic recording material layer coupled to the plastic substrate is exposed to an interference pattern formed by at least one coherent light source. At least a portion of the barrier layer is dissolved.
The foregoing is a summary and thus contains, by necessity, simplifications, generalizations and omissions of detail; consequently, those skilled in the art will appreciate that the summary is illustrative only and is not intended to be in any way limiting. As will also be apparent to one of skill in the art, the operations disclosed herein may be implemented in a number of ways, and such changes and modifications may be made without departing from this invention and its broader aspects. Other aspects, inventive features, and advantages of the present invention, as defined solely by the claims, will become apparent in the non-limiting detailed description set forth below.